Lose Weight and Stay Sane This Season! The Energy Balance Equation

Shed pounds without destroying your health

By Michael Ormsbee, PhDFlorida State University
Edited by Kate Findley and proofread by Angela Shoemaker, Wondrium Daily

Some people take “calories in, calories out” too literally, believing they must go on a starvation diet to lose weight and look good. Professor Ormsbee explains why this is counterproductive.

Weight loss concept wit weights fruit and heart
When reducing calorie intake to achieve weight loss, it’s important not to be too extreme in the number of reduced calories or muscle mass will be lost. Photo By Isarat / Shutterstock

What Is the Energy Balance Equation?

You can manage your weight with the energy balance equation. This equation consists of three conditions: energy balance (the calories you take in match the calories that you expend or burn), positive energy balance (you eat more calories than expended), and negative energy balance (where more energy is expended than you take in). 

Theoretically, if you are in energy balance, you will not lose or gain any weight. In a positive energy balance, you will gain weight, while in a negative energy balance, you will lose weight.

Either way, whether positive or negative energy balance, numerous changes occur to your body—cellularly, metabolically, and hormonally—to facilitate weight gain or loss. As an example, let’s consider extreme weight loss where morbidly obese people are placed on medically supervised diets as an alternative to gastric bypass surgery. Morbidly obese is defined as a body mass index (weight to height ratio) above 40, or having over 100 excess pounds (lbs) of fat. In this example, a female who is five feet tall might weigh 205 lbs or more.

When put on very low-calorie, medically monitored diets of 800 calories per day—which believe it or not is the common medical treatment at bariatric centers in the United States—the individuals lost a massive amount of weight. On average, about 40 lbs or more is lost in an approximate 12-week treatment period. 

Downsides of Low-Calorie Diets

Here is the problem, though. That weight loss is not only coming from fat. In this example, the 40-lb weight loss is usually about 75% fat and about 25% muscle. 

“That 25% loss of muscle mass is not desirable; and for this reason, new research, including my own, seeks ways to modify these medically supervised, very low-calorie diets to get the most weight loss from fat while keeping as much muscle as possible,” Professor Ormsbee said.

Keep in mind that an 800-calorie diet is only recommended under medical supervision. For the average person, Professor Ormsbee suggests dietary strategies to improve weight loss without sacrificing muscle. 

This includes regular exercise and some specific dietary habits, such as increasing protein intake. Regardless, when it comes to energy balance, we should pay attention to how many calories we eat and drink to begin losing or gaining weight, and the patterns may surprise you. 

The 3,500-Calorie Rule

Let’s start with a simple question: How many calories do you need to cut from your diet to lose weight? Taking it one step farther, how many calories will it take to lose just one pound?

For years, textbooks and experts have asserted that one pound of fat is equivalent to 3,500 calories. Thus, if you aim to lose one pound of fat per week by modifying your diet alone and not considering exercise, then you would eat 500 less calories per day for one week. That’s pretty easy to wrap your mind around; just skip a daily dessert or an extra serving at dinner.

You might start thinking that if you eat 500 calories less per day and lose one pound per week, you could up this to a reduction of 1,000 calories per day and lose two to three lbs per week. However, the more is better mantra does not always suit us well with diet and exercise. 

Recall the example about weight loss coming from both fat and muscle. It turns out that if your energy deficit is over about 1,000 calories per day, it is generally not well tolerated. This is due to many factors, but primarily when you drop your calories by too much, you will also lose muscle—which you do not want.

Too great a calorie deficit also runs a greater risk of missing out on key nutrients, like your vitamins and minerals, and you would likely see your energy levels drop and your fatigue increase. Not to mention, you’ll probably feel hungry. 

One myth that has arisen from this 3,500-calorie rule is that weight will simply continue to drop at the same rate, otherwise known as the linear model of weight loss. In an article in the International Journal of Obesity, the authors studied the accuracy of the 3,500-calorie rule. As it turns out, the rule actually overestimates weight loss, meaning that 3,500 calories may translate to less than one pound lost.

Thus, an update was made. The new model for weight loss, called the thermodynamic model or simply the dynamic model of weight loss, takes into consideration your baseline body composition, age, height, sex, and degree of calorie restriction. This model results in a curvilinear pattern of weight loss over time rather than the traditional linear model of weight loss, and is much more accurate in actual trends for weight loss. 

This article was edited by Kate Findley, Writer for Wondrium Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for Wondrium Daily.
Dr. Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University.

Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his MS in Exercise Physiology from South Dakota State University and his PhD in Bioenergetics from East Carolina University.